The objective of this proposed research is to develop a guinea pig model for studying changes in pituitary-adrenal activity during mother-infant separation. Involuntary separation of infant primates from their mother for even a brief period produces a number of physiological consequences, including a marked increase in the activity of the pituitary-adrenal system. This phenomenon is of interest for a number of reasons, but research in this area has been impeded by the lack of a viable rodent model. Based on similarities between guinea pig and primate young in terms of attachment and other developmental processes, it appears that the guinea pig is the most promising candidate for this rodent model. We will assess the merit of the guinea pig model by determining if brief, involuntary separation produces pituitary-adrenal activation as measured by elevation of plasma cortisol levels. This response will be studied in mother-reared infants, in the mothers of infants, and in infants raised from birth with inanimate "surrogate mothers". In all instances, the relationship of the cortisol response to behavioral signs of distress will be examined. A rodent model will contribute to our understanding of the consequences of separation and the process of attachment, and in addition, will reduce the demand for primates in this field of research.